The present invention relates to elevator systems. More particularly, the invention relates to various embodiments for terminating a tension member.
A conventional traction elevator system includes a car, a counterweight, two or more tension members interconnecting the car and counterweights, terminations for each end of the tension members at the connection points with the car and counterweights, a traction sheave to move the tension members, and a machine to rotate the traction sheave. Alternatively, 2 to 1 roping configurations are also common and typically include a car, a counterweight, two or more tension members interconnecting the car and counterweights, terminations for each end of the tension members at structural support points, a traction sheave to move the tension members, idler sheaves to interconnect the counterweight, the car and the traction sheave, and a machine to rotate the traction sheave.
The tension members have traditionally been formed of laid or twisted steel wire. Termination of such tension members at the car and counterweight in a traction elevator system, or, alternatively, at the structural support points for a 2 to 1 roping configuration elevator system, is conventionally effectuated by means such as compression terminations and wedge terminations.
Compression terminations of the prior art, which have been employed for ropes with an aspect ratio of one (round) and ropes with an aspect ratio of greater than one (flat) provide a reasonably broad range of pressures. However, even a simple compression termination requires multiple components, thereby making such a termination device relatively expensive to manufacture and time consuming to install. Wedge-type termination devices have also been employed for both round and flexible flat tension members and are effective, yet remain relatively expensive to manufacture.
Furthermore, with conventional termination devices, the pressure or holding force is exerted upon a portion of the tension member or rope equivalent in length to the holding surface of the device. Thus, for effective holding force, the length of the holding surface must be great enough to maintain the load.
Thus, the art is still in need of a reliable termination device that reaches an advantageous price point, is easy and timely to assemble, is easy and timely to disassemble and decreases clearance requirements.
The termination device of the present invention is a body having a particular configuration which facilitates a tension member being wrapped therearound for termination. In one embodiment, one end of the tension member is inserted in an aperture upon the body. The insertion does not intentionally hold any of the load force of the tension member (from a car or counterweight hanging thereon) but merely retains the tension member in position while the member is being wrapped around the termination device. The tension member is terminated (i.e., maintained in position during its working life) by friction of the tension member against the termination device (in the first wrap) and by a clamping force on the tension member provided by the member itself as it overlaps the first turn in the second partial wrap of the tension member through the clamping force and the frictional forces produced, all of the load force is reacted out of the system before reaching the end of the termination member inserted in the aperture.
In a preferred embodiment of the present invention, the body has a cylindrical surface.
The device of the present invention reliably terminates a tension member while using less material and requiring less clearance.